1. Field of the Invention
The present invention relates to a golf club head and, more particularly, to score lines on the face.
2. Description of the Related Art
Generally, on the face of a golf club head, a plurality of straight grooves are formed parallel to each other in the toe-and-heel direction (e.g., Japanese Patent Laid-Open Nos. 10-248974 and 2005-169129). These grooves are called score lines, marking lines, face lines, or the like (to be referred to as score lines in this specification). These score lines have an effect of increasing the back spin amount or suppressing a significant decrease in back spin amount of a shot in a case of a rainy day or a shot from rough. As a method of forming score lines, for example, cutting, forging, or casting is used.
The width of a score line is narrow and, for example, that of a score line of a golf club head for competitions is determined to be 0.9 mm or less by the rule. It is not always easy to form a plurality of score lines to be straight and parallel to each other. For example, when forming score lines by cutting, the score lines may be slightly distorted due to the shake or wear of a cutting tool or distortion of the material of the face. In case of forging, score lines may be slightly distorted due to the influence of distortion of the material of the face. In case of casting, score lines may be slightly distorted due to shrinkage. When score lines are distorted, their outer appearance becomes poor. In addition, individual difference in performance between the products may occur.